


Beyond the ghost trees

by CastielsCarma



Series: Kinktober 2020 [7]
Category: Supernatural
Genre: Alien!Cas, Alternate Universe - Science Fiction, Egg Laying, Kinktober, Kinktober 2020, M/M, Suffering Dean Winchester, Tentacles, Top Castiel/Bottom Dean Winchester
Language: English
Status: Completed
Published: 2020-10-07
Updated: 2020-10-07
Packaged: 2021-03-07 21:47:48
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Rape/Non-Con
Chapters: 1
Words: 3,814
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26884621
Author URL: https://archiveofourown.org/users/CastielsCarma/pseuds/CastielsCarma
Summary: Dean goes for a walk to look at the alien planet scenery. Then he stumbles upon somethingveryalien.
Relationships: Castiel/Dean Winchester
Series: Kinktober 2020 [7]
Series URL: https://archiveofourown.org/series/1949407
Comments: 13
Kudos: 92
Collections: Kinktober 2018





	Beyond the ghost trees

**Author's Note:**

> This is my prompt for day 7 of Kinktober: Rimming, breeding, or **tentacles**.
> 
> Apparently, I'm back to writing dark stuff. So, this is dark. Dean suffers. Read the tags and enjoy.
> 
> Kudos and comments are as always appreciated. I love to hear from you guys. =)

Dean adjusted his med-pack that was strapped across his back, then his fingers casually brushed over the plasma gun that was attached to his hip. “'Don't go walking in the forest alone, '” Dean mimicked in his brother's voice as he picked up a peanut butter snack from a small pocket.

He squeezed the peanut butter into his mouth with a soft sigh. He hadn't been walking for long – just a mile – but he was hungry. He'd skipped lunch thanks to Sam insisting that he had to have those flower samples right that instant. 

Dean didn't get the hurry. He was walking in an entire forest filled with the tiny, blue flowers that emitted that weird pulsating light Sam was curious about. The light kept some kind of rhythm because the flowers all flashed at the same time but that was for Sam to figure out why. 

He avoided touching the white ghost trees that grew near the flowers. They were not as common as the flowers but they freaked him the fuck out. On the second day of the mission, Dean had stumbled – it happens – and braced himself on a tree, only for it to literally dissolve into a puff of something. Tiny, white specks of dust had landed on his suit and Dean had been so freaked out that he pressed the button on his helmet. Even as the shield covered his face, Dean had to sit down and wait for his panicked heart to slow down. 

He was just the pilot, not a sciency kind of guy. Sure he was smart, but he didn't care squat about pigeons, or why the sky was red sometimes or which species of ant ruled supreme. Question him on ancient Earth lore – especially in the music and early pre-hologram show and Dean would ace it.

Dean squeezed out the last of the peanut butter and stowed the wrapping in his thigh pockets. Spacesuits – just all the pockets on them made Dean love them. He'd seen the history books and movies, with the ancient suits of old. They seemed big and clunky and totally uncomfortable. Those dudes couldn't even use their hands properly. Dean flexed his fingers with ease. The flowers would be fresh potpourri if he'd tried to do something similar with that old gear.

The white ghost trees gave way to – for lack of a better word – the blobs. He was sure that Sam had a scientific name for them but to Dean they were blobs. He knew they were specific to this very region – satellites had shown that sure, they could be found growing around the entire planet – but this was the region with the highest concentration by far. “Why is that, Dean? What are the blobs made of? Why do they keep dying when we try to study them? Are they connected to the flowers, they're a tinted with blue?” Dean had just shrugged and given Sam a look that said he was the science guy so he better get going science-ing. 

The blobs varied in size but they were all see-through and had an almost mist-like quality to them. Dean was not touching them either, not unless he was ordered to do so. He was on an alien planet and everything was... well, alien. 

Sam was heading out later with some of his nerd-friends, Kevin and Donatello who were equally excited by the blobs. They could examine, Dean was just out for a stroll. 

He found a place that was relatively blob-free, on higher altitude, and climbed up. There was some kind of moss that covered the rocky outcrop but it seemed so home-like that Dean didn't mind stepping on it. 

He exhaled and looked out over the eerie landscape. The two moons were still up and would be up for another day but Dean could feel a dense feeling settling over him. He had been up for over ten hours, so he figured he'd give it some more and then catch some sleep. 

Ghost trees covered the ground beneath him, like cold eerie white fingers reaching out to the sky as far as the eye could see. He was not sure if they were reaching out in reverence or crying out for help. He'd go with the latter. Creepy ghost trees did belong in the crying category.

Dean hoisted out the wrapping for his peanut-butter snack and tossed it over the edge of the outcrop. It singled down and landed on a ghost tree. It took far longer than usual, Dean counted three whole seconds until the tree vanished in a puff of weird tree-dust.

Intrigued, Dean searched in his suit for something else he could toss. He found an old rock-specimen from a trip he and Sam had done two years earlier to Eldon Prime.

Dean shrugged and tossed the rock. 

It landed on a ghost tree. 

Dean waited and waited. 

Nothing. 

That was odd, he was sure that he hit the tree and not the ground. Still, the tree refused to explode into Casper-bits.

Dean took another step towards the edge to get a really good look at the tree when he felt the ground give way. 

He screamed as he fell down and instinctively reached out to grab something. He caught the branch of a ghost tree and was relieved for a very brief second until he realized why they were called ghost trees. 

The tree dissolved underneath his fingers and Dean plummeted to the ground. 

He hit the side of the rocky outcrop once and sharp pain exploded in his back. 

He tried to make himself small as the ground approached but the impact still jolted through his body. Adrenaline was coursing through his body and Dean exhaled in short puffs. With a groan he rolled over, only to find the ground give way again.

What the hell?

Dean screamed as he fell into darkness. 

He landed on his side with force and exhaled harshly as he felt his whole chest area constrict. It was as if someone had wrapped him into a steel corset and tightened it.

Dean laid still and tried to breathe but all that came out was a low pained grunt. After what felt like an eternity, he could finally take a deep breath although it still made his ribs echo with throbbing pain. 

He looked up at the sky. It was the same star-filled black space he'd seen before but as he turned to the side, he didn't see ghost trees and weird blobs but rather what looked like stone and rocks. 

That was just his luck. Going for a walk, enjoying his snack, and falling into a pit of doom. And his helmet had a crack in it.

Dean got up slowly and tried hailing Sam on the com. “Sam, you there? Can you hear me?” His only reply was static. Just fucking great.

He pushed down his sudden worry and decided to explore the cave or whatever the hell he was. There was no way in hell, he would be able to climb back up again. He had a flare gun that he could use but that meant someone had to see the flare.

He had only taken a few steps inside, rounding a corner in the cave when a blue-ish light greeted him. It cast blue shadows on the walls, that Dean had to confess were really pretty, but again – weird alien blob. He wasn't touching that thing, even if the shine seemed more intense here. 

Dean chuckled. Of course, it felt more intense. He was in a goddamn dark cave. 

Suddenly Dean cursed out loud. The Panicake! 

It was a small round emergency emitter. When you were in trouble, you were supposed to press it and a signal was sent to the ship with the exact coordinates of your position. It was also yellow and round; thereof the Panicake.

Dean pulled off his gloves and reached into a pocket. Bingo. Round, sweet, and full of promise. 

Just as he was about to press the button, a blue light flashed in the cave. 

Dean's Panicake slid out of his grip and landed on the ground with a thunk. 

That light... it was strange. Strangely beautiful. 

Dean took a step towards the light before turning his head the other way. There was something that he was about to do, something important. 

He tried to recollect the events of why and what that important thing would be but came up empty.

As Dean continued walking deeper into the cave the strange blobs were everywhere. They covered the ground, the walls of the cave and maybe it was just the darkness in the cave but they seemed to shine brighter.

Dean finally stopped in a hall of the cave. It expanded into two different directions. Dean clicked his tongue, wondering if he should go further in or just wait there. The blobs started pulsating. 

Dean decided to stay.

Dean.

Something was behind him. Dean's eyes flashed open. He'd been dozing off. A tiny voice in his head whispered that he should be alarmed by that, that he should run. 

Dean.

The other, louder voice was much more insistent, commanding. 

Dean turned. His eyes widened in surprise as he saw the man standing there. What was he doing there, and more importantly why?

The flashing lights of the blobs had stopped but Dean couldn't stop looking at the man. He commanded attention. 

He looked human – a handsome human to boot – with his dark, disheveled hair, full lips, and strong jaw. Dean thought he saw some stubble on his cheeks but it was difficult to focus on the stubble when his sculpted and naked chest was just there. 

“Hello, Dean.”

Dean blinked. How did he know his name? 

The man took another step and smiled at Dean. “It's been a long time.”

A cold shiver went through Dean even as his mind tried to decipher the words. It was like they were internal which didn't make sense at all but the handsome guy – fine, he was hot as hell – looked calm, so Dean figured he'd be calm too.

“Oh, I sense you're confused.” He smiled again, showing white teeth. “Allow me to help.” 

The man touched Dean's forehead.

He got overwhelmed with clarity but it didn't make sense because Dean didn't know jack shit. He just knew that he needed to run, run, run. He needed to get away from this person – no, not a person, a thing – an old, ancient knowing that drummed inside him to the same beat as danger. 

Dean turned to just do that when he felt something heavy slide across his back and he was suddenly pushed forward. Towards this man-not man.

“I'm Castiel.”

Dean screamed as he felt something slither around his ankle. He shook his foot frantically as another something crawled down over his shoulder. “Get off me!”

His foot was pulled down and finally, Dean looked and looked and a hysterical curse bubbled out of him. It was a fucking black tentacle. 

His mind flashed to all the old hentai porn he used to jack off to but this was nothing, nothing like that. If hentai porn was the candle, this Castiel was the terrible, burning sun.

Castiel walked up to Dean slowly and even though he was definitely not human, he looked human. The tentacle over his shoulder crawled inward and hooked itself underneath his arm. 

It was a fucking tentacle. 

Primal fear took over. 

Dean pulled away from Castiel and yanked his foot free. 

Castiel's eyes – blue, wide and so human it hurt – widened in surprise but Dean was already ahead of him. He grabbed his gun – and never had anything felt so right in his life – aimed and squeezed the trigger. 

The shot hit Castiel in the chest; echoes bouncing off the walls of the cave until Dean thought the sound would never end. 

“You shouldn't have done that, Dean. I like my mates to be powerful, yes, but obedient.”

Something grabbed him and pushed. 

Dean grunted as his back slammed into the cave wall. 

Castiel was already there, like he'd teleported. Four tentacles reached out, each ensnaring his ankles and wrists. 

“You are covered in non-biological material. This will hinder reproduction.”

Chills went through Dean. “You let me go you fucker. I'll – “

Castiel placed his hand on Dean's cheek.

Dean snapped his mouth shut. Pure horror seized him and if he thought he knew Castiel, knew the outcome, knew anything, that single touch proved him wrong. It was warm and inviting and terrifying.

Another cursed black tentacle came from Castiel's back somewhere and he pressed it all over Dean's body, his chest, arms, chest. Further down his legs and boots. 

Agonizing pain bloomed on Dean's skin and then the tentacles were gone. 

Castiel's voice was smooth, amused as he spoke. “Or you'll do what?” He grabbed Dean's helmet with his hands and pulled it away. It landed with a clonk on the cave floor. 

Dean held his breath for as long as he could but soon he started trashing. 

The tentacles around Dean's wrists and ankles tightened. 

Black spots danced just outside Dean's vision when Castiel grabbed his hair and yanked him toward himself. His mouth was on Dean's and he kissed him angrily even as Dean tried to pull away.

Castiel let him go. “I am generous when I want to be.”

Dean's lungs filled with blessed air. Castiel had done something so he could breathe without his helmet.

“What do you want, you – “

Dean got the answer soon enough when three tentacles snaked around his body. They ripped his suit with ease before disappearing again.

Even as Dean strained against the bonds he felt two more tentacles snake around his legs. They pulled his legs apart. 

Dean felt bile rise in his throat and despite all his clawing and cursing, a shiver went down his spine. No, no, no.

Castiel cooked his head. “I do eat all the time. This soil sustains me well. I am vast, and a multitude. All over. It's just that I'm the biggest here.” He wrapped his hand around Dean's throat and squeezed.

Dean felt the tightness as Castiel pressed on slowly. Not until Dean trashed against the tentacles, did he let up. He coughed, a raw sound as he gulped down air.

“It's time I get bigger.”

Dean couldn't comprehend the odd statement, not until he felt a smaller tentacle – he almost laughed hysterically at how many sizes these tentacles came in – wrapped around his underwear and yanked. 

His cock was small and shriveled up but that mattered little. A small, much thinner tentacle wrapped around Dean's cock and started pulsating.

“No, stop, please. I can't – “ Dean's next words were lost in a vortex of pain as Castiel wrapped the tentacles tighter around his wrists. The smaller tentacle around his cock seemed to want to try to chase that pain away. It pulsated more and soon it landed on Dean's head. 

Dean thought he'd found some reprieve when his head felt a sharp, sucking motion. He moaned out loud, the sound dragged from him, and his knees buckles. The cursed tentacles were there to catch him.

“You seem very sensitive there. “

“Fuck you,” Dean panted.

Two tentacles slithered up his chest until they found his nipples. Dean tried to back away but soon a small suction cup on the tentacles had him writhing in pain, pleasure, it was all lost to him. 

The center of Dean's world was his cock, pulsating with need and his nipples raw and aching from all the sucking. “Please, get them off.”

Castiel just looked at Dean. “No, you and I will breed. I do think getting you off is a requirement then. I'm not knowledgeable about human anatomy.”

Dean wanted to laugh at the absurdity. A goddamn tentacle monster was fucking him senseless while knowing jack shit about humans. 

Fire pooled inside him, an orgasm that threatened to take him under. His breathing was shallow and fast and for a quick moment, he feared that whatever fuckery Cas had done to him to make him breathe had started to fade. 

A smaller tentacle hovered around his perineum and as Dean felt that cold slither, he came hard. Come shot out of his cock, hitting Castiel on the chest. 

Dean sagged in Castiel's grip, tired, empty, and spent. His words that sounded strong in his mind were pleading and hollow out from the confines of his raw lips. “Now... please, can I go...”

Castiel stroked Dean's chest with his hand and flicked Dean's nipples. 

He yanked away in pain; they were too raw and sensitive. 

“The breeding is not done yet. Open.”

Dean was tired, afraid, and confused. Castiel seemed relentless, a never-ending nightmare and Dean feared that he would be fucked to death. “What..?”

A tentacle slithered around his lips. The taste was vile. Dean turned to the side. Tears came to his eyes as his stomach cramped. He puked on the cave floor. 

The sharp pain on his cheeks shocked him to his sense. It seemed so mundane, so human after everything else to receive, and for a deranged moment he wanted to lean into Castiel's touch. At least his hands were human.

“I said open.” 

The tentacle that had previously probed slowly, almost playfully thrust inside Dean's mouth. 

Dean choked on the tentacle as tears sprung to his eyes. 

Castiel pushed the tentacle in and out of his mouth, slowly, too slowly. 

Dean could taste everything. Bile threatened to come up and he was not sure what would kill him first. Either he'd choke on Castiel's tentacle or he'd suffocate on his own puke. 

Finally, Castiel eased up and retracted from his mouth. 

Dean spat but one breath, one taste and he bent over as much as he could and emptied his stomach on the floor. 

“Mm,” Castiel hummed.

Dean was in a daze and didn't even have the energy to fight Castiel any longer, let alone try to decipher what he fucking meant with that murmur. 

Again a tentacle was on his cock and Dean tried to yank away but tentacles on his wrists pulled him forward. 

Castiel grabbed his chin with a strong hand, almost too the point of pain. But what was one pain against another? “You're strong. Stubborn. Still defiant. Your vessel is perfect for my young.”

Dean shook his head in mute protest. 

Castiel smiled.

A purple tentacle rose from Cas. Dean's eyes almost rolled back and he yanked on the tentacles around his wrists but it was like moving a mountain. Castiel didn't budge.

His legs were pulled apart again and Castiel shifted his hold on his wrists. 

Dean had to readjust his balance and leaned forward.

“That will do.” Castiel's voice had taken on a note of eagerness. Dean didn't like that at all.

He froze as he felt what had to be that awful, purple tentacle press between his cheeks. It was a small nudge at first, almost gentle. His cock started growing again as blood rushed to all the wrong places. He'd rather it rushed right out of him. Death couldn't come fast enough. 

He tensed as the tentacle started pushing in. All it did was make his ass tighter but Castiel didn't care. 

The tentacle breached his ass and Dean shouted out as a ring of fire consumed him. His heart beat so fast that it almost overshadowed his screams. A black tentacle was jammed down his throat and staying there, unmoving. 

“I think I do like those tears from your eyes. “ 

Dean breathed out harshly through his nose. Drool had already started to spill from his mouth. He tried to plead with his eyes for Castiel to stop even though he knew that it wouldn't help.

The purple tentacle pushed further in Dean's ass. 

He tried to get away even stand on his toes but Cas was relentless. 

Dean thought he would burst. The tentacle in his ass was too big, too much and his asshole would tear and he'd die there in this fucking cave fucked to death – 

He screamed out as Castiel started moving the tentacle. The tentacle in his mouth muted the worst of the screams but it was not enough. 

The tentacle in his ass continued to fuck him and Dean was on fire. He could feel it push inside him and it was so big that his ass clenched around it. 

He chocked on the tentacle in his mouth then and Castiel removed it quickly. Dean coughed and took a huge gulp of air. “Castiel, I'll do – “

Castiel shoved his tentacle back into Dean's mouth and pulled him close to his own body. The tentacles still held him there in an iron grip. 

Dean's stomach churned being so close to Castiel and that he was participating in this mockery of an embrace. He moaned around the tentacle in his ass as it continued to fuck him relentlessly He could feel it inside him, pushing so hard that his stomach bulged. 

Bile rose again and Dean swallowed down in a panic. He would not die like this. His toes curled in sharp pain as his asshole stretched again. 

Dean didn't know when it happened amount the countless thrusts of Castiel's tentacle in his ass fucking him raw but soon he had his hands wrapped around Castiel's biceps, clinging to life. 

Castiel didn't even bother to hold him up with the tentacles anymore, instead, he allowed him to lean on him. “Now, Dean, it's time.”

Dean blinked and looked up at Castiel's eyes. He wished there were no time at all, only oblivion and darkness. Instead he found that cursed, blue light looking back at him.

He could feel the tentacle inside him swell even more. Dean sobbed out a cry as something emptied inside him, a warm liquid that was never-ending. It ran down his legs, sticky and gross but inside his ass, the tentacle swelled and grew until he thought, that this was finally it. 

His hole was warm and swollen and a sudden contraction in his ass had his knees buckling. Tears welled in his eyes. He was so tired.

Castiel lowered him down to the cave floor; his tentacles finally gentle. 

“The attachment of the egg sacks will take awhile. Rest.” Castiel reached out and stroked Dean's cheek with too human hands. 

Dean moaned against another contraction as the tentacle in his ass swelled. 

“Shh, you're so strong. Let me ease you in. The egg sacks are the final step in the breeding process.”

Castiel grabbed Dean's soft cock with his hand and started stroking it. Soon it was blood filled again, purple and hard. 

Dean cried as another contraction in his ass rolled through him. 

“You're so good, Dean.” Castiel smiled, never letting go of Dean's cock.


End file.
